The present invention relates to a binary input circuit and more particularly to an apparatus and method for controlling a threshold voltage of a binary input circuit of an integrated circuit.
Integrated circuits are designed using standard cells from a standard cell library. Standard cell libraries are not readily developed. Rather, such libraries must be laboriously worked out transistor by transistor and cell by cell by the designers. A typical library development cycle consists of defining the physical sizes of the devices, specifying the desired performance parameters, e.g. speed, noise margin, etc., designing the cells, simulating the cell designs, making prototype integrated circuits using the cell designs, and measuring the actual characteristics of the prototype integrated circuits. Usually the characteristics are used to go back and revise the design of various cells so that the desired performance parameters are met. This revision requires a second prototype set of integrated circuits and a measurement of the characteristics of the revised integrated circuits.
One of the more important cells in a library is the pad input cell. One of the harder things to do is design a library that is manufacturing process independent.
It is an object of the present invention to provide a highly stable highly accurate voltage reference circuit that sets a highly stable and highly accurate threshold voltage for a plurality of binary input circuits.
It is another object of the present invention to provide a process for producing an integrated circuit with a plurality of binary input circuits, each having its threshold voltage set by a common reference voltage circuit.